Glass sheets may be bent and tempered at high production rates on a bed of arcuate forming rods. In this process individual glass sheets are conveyed without stopping through heating, bending and tempering zones on high speed glass sheet conveyors.
The apparatus for shaping the glass sheets comprises a series of forming rods each of which has a central section curved to a desired arcuate form. On each side of the curved section there is a straight section of rod, the two sections being aligned with each other on an axis which is a chord of the arcuate section of the rod. Suitable bearings permit rotation of the rod on this axis. The individual rods are mounted in a frame so that their axes are parallel and extend transversely of the direction of travel of the glass sheets. Typically, the rods are interconnected for pivoting in unison, each about its own axis, from a first position wherein the curved sections and rotational axes of all the rods lie in a common plane to a second position wherein the curved sections conjointly define a curved surface whose transverse curvature varies with the angle of rotation of the rods.
Each curved forming rod is surrounded by a tubular sleeve or roll made of stainless steel which possesses substantial torsional strength but is flexible in its axial direction. The sleeve is rotatably mounted on the curved rod to permit rotation regardless of the inclined position of the curved rod. The sleeve is coupled at one end to a pinion which is connected to suitable drive means. As a softened glass sheet is advanced over such rolls, it assumes the shape of the surface defined by the rolls. This shaping of the sheet may be effected either by gravity when the softened glass sheet sags under its own weight or by pressure applied by a counterform. The details of different types of such forming apparatus are set forth in U.S. Pat. Nos. 3,545,951, 4,054,437 and 4,054,438, all of which are incorporated herein by reference. Details of the construction of the rolls are set forth in U.S. Pat. No. 3,831,239 which is likewise incorporated herein by reference. As will be apparent from these patents transverse curvatures may be formed in glass sheets either by raising the central portion of the sheet as in the '951 and '437 patents or by lowering the outer edges of the sheet as in the '438 patent.
The foregoing systems are very satisfactory if the glass is to be bent in one direction only. They are not suitable, however, for producing glass sheets having a compound curvature composed of curves extending in two directions, such as are used in the automotive market.
Apparatus for forming glass sheets with compound curvatures extending both transversely and longitudinally of the sheet is described in U.S. Pat. No. 3,409,422. Such apparatus uses a gas support bed for the glass sheet. The apparatus, however, requires long and difficult adjustments in order to change the radii of curvature of the sheets.